Where is bank 1 sensor 1 02 sensor on a 2003 Qx4?

On a 2003 Infiniti QX4, the Bank 1 Sensor 1 O2 sensor is located on the exhaust manifold, upstream of the catalytic converter. This sensor measures the oxygen content in the exhaust gases before they enter the catalytic converter, helping to regulate the air-fuel mixture for optimal engine performance. To access it, you may need to lift the vehicle and work under it, as it's positioned close to the engine.